The invention is directed to a self-contained apparatus for use in determining the presence or absence of a biological or chemical substance within a test environment. Prior art tests for determining, for example, the presence of chemical substances or micro-organisms in water and air or the effectiveness of steam or gas sterilization equipment typically require rigid standardized procedures which can only be performed by highly qualified personnel.
A common test for sterilization effectiveness is performed by a technician who first places an absorbent paper test strip which is impregnated with a predetermined number and species of live micro-organisms in a sterilization chamber along with certain objects to be sterilized. The test strip and the objects are then subjected to a sterilization medium such as steam, gas or radiation. Once the sterilization cycle is completed, the technician removes the test strip from the sterilization chamber and places it in a sterile culture medium. The micro-organisms on the test strip are then incubated in the culture medium for a predetermined period of time. The technician then examines the medium to determine whether any micro-organisms on the test strip survived sterilization. Any observable change in color, appearance or turbidity etc., of the medium may indicate that sterilization was not successful.
This above-described sterility test can only be carried out by a skillful technician who is capable of avoiding contamination of the test strip during the various manipulative steps of the test. Similarly, other known tests for the presence or absence of a chemical or biological substances in a test medium requiring the manipulation of a test article require skill to avoid contamination of the test article during the test procedure.
The present invention is a self-contained test apparatus which eliminates potentials for contamination during the test procedure described above. The invention also presents solutions to shortcomings encountered by self contained test apparatus known to applicants;
U.S. Pat. No. 3,440,144, assigned to H. W. Anderson Products, Inc., relates to a package containing a spore strip, a frangible ampule containing a culture medium, a flexible sleeve, and a flexible semi-permeable bag. The frangible ampule has an open spout connected to the body of the ampule by a neck. Sterile culture medium is placed within the ampule through the opening in the spout. The spout is heat sealed, forming a closed ampule. The ampule is then sterilized and placed within the flexible sleeve along with the spore strip. The sleeve is then placed within the flexible bag and the ends of the bag are heat sealed. The bag is then placed in the sterilization chamber along with the objects to be sterilized. Once the sterilization cycle is completed the technician removes the bag from the chamber, grasps the sleeve containing the ampule and spore strip through the bag, and breaks the spout off at the neck of the ampule releasing the culture medium but avoiding tearing the sleeve and the bag with the shards of the ampule. The bag is placed in an incubator for a predetermined period of time. The technician then examines the medium to determine whether any micro-organisms survived the sterilization cycle. The technician must use care throughout this test in order not to prematurely break the ampule or rupture the flexible, semi-permeable bag. A further disadvantage, not dependent upon the skill of the technician, is apparent in using this sterility test. During the sterilization cycle, the sterilant permeates the bag and kills the micro-organisms. However, not all the sterilant passes through the bag. The bag entraps and retains some of the sterilant. After the bag is removed from the sterilization chamber the sterilant continues to diffuse from the bag into the culture medium. The additional sterilant in the culture medium may inhibit and kill the growth of any micro-organisms that have survived the sterility test. Thus, there is a danger that the test apparatus will show a false sterility result.
The U.S. Pat. No. 3,440,144 also relates to a flexible permeable bag sealed at both ends. Culture medium is sealed in one end of the bag and a spore strip is sealed in the other end of the bag. The bag is placed in the sterilization chamber along with the objects to be sterilized. After the sterilization cycle is completed the technician removes the bag from the chamber and squeezes the end of the bag containing the culture medium. The culture medium is forced into the end of the bag containing the spore strip. The bag is then placed in the incubator for a predetermined time, and observed for signs of micro-organism growth. A disadvantage to this test is that the bag does not provide for the direct exposure of the spore strip to the sterilant when the bag is in the sterilization chamber. The bag acts as a shelter for the micro-organisms and may allow some of the micro-organisms to survive the sterility test.
The U.S. Pat. No. 3,661,717, assigned to the Minnesota Mining and Manufacturing Company, and marketed as "ATTEST", relates to a sterility indicator containing a spore strip, a frangible ampule containing a culture medium, a flexible tube, and a gas permeable cap. The spore strip and the ampule are placed in the tube. The ampule fits snugly within the tube such that very little of the volume of the tube is unoccupied. The gas permeable cap is placed over the open end of the tube. The tube is then placed within the sterilization chamber along with the objects to be sterilized. Once the sterilization cycle is completed the technician removes the tube from the sterilization chamber and pinches the tube between the thumb and forefinger crushing the ampule and releasing the culture medium onto the spore strip. The tube is then placed in an incubator for a predetermined time and observed for signs of micro-organism growth. A disadvantage to this prior art is that the cap does not provide for direct exposure of the spore strip to the sterilant when the tube is in the sterilization chamber. Some of the micro-organisms are sheltered and may survive the sterilization. The survival of micro-organisms after the sterilization cycle indicates that the other objects in the chamber were not completely sterilized. When the sterilant does not penetrate through the cap sufficiently to kill the micro-organisms and micro-organisms survive, a false indication of non-sterility results. Another disadvantage to this prior art product is that the lack of a real seal causes the medium to leak through the gas permeable cap after the ampule has been crushed.
The U.S. Pat. No. 4,304,869 and marketed as "PROOF" by American Sterilizer Company, Inc., includes a spore disc, a glass ampule containing a culture medium, a tube having one open end, and a cap containing downwardly extending legs. The spore disc and the ampule are placed within the tube. The ampule fits snugly within the tube. The cap rests on the open end of the tube. The legs on the cap extend into the tube and abut the top of the ampule. The tube is then placed within the sterilization chamber along with the objects to be sterilized. Once the sterilization cycle is completed the technician removes the tube from the sterilization chamber and pushes the cap down on the tube. The legs on the cap exert a force and crush the ampule releasing the culture medium onto the spore disc. The product is then placed in an incubator for a predetermined time and observed for signs of micro-organism growth. However, since the legs on the cap must be long and thick enough to have sufficient force to crush the ampule, the tube must be long in comparison to the length of the legs.
Another prior art product, European patent application No. 78,112, assigned to the American Sterilizer Company relates to a sterilization indicator containing a rigid plastic container holding a spore strip, a breaking wire and a frangible ampule holding a liquid nutrient medium and a dye to indicate any spore growth, and a cap. The spore strip is located at the bottom of the container along with the breaking wire. The frangible ampule fits snuggly within the container and rests on the breaking wire. A cap is positioned over the top of the container and defines an access path to the exterior so that the sterilant cannot enter the container. The container and cap are placed in the sterilization chamber along with the objects to be sterilized. Once the sterilization cycle is completed a technician removes the container from the sterilization chamber and moves the cap in a direction towards the ampule. A central recess portion on the cap exerts a force and crushes the ampule releasing the culture medium onto the spore disc. The container is then placed in an incubator for a predetermined time and obsered for signs of micro-organism growth.
In the above described prior art products, the spore strips tend to settle or are deliberately placed at the bottom of the tube and become lodged between the lower closed end of the tube and the lower end of the frangible ampule. The close adjacent relationship of the spore disc with the bottom portions of the tube and ampule cause a "dew point" factor, when the tube is exposed to the sterilization process. The "dew point" factor, caused by the formation of condensation at the bottom of the tube adjacent the lower end of the ampule, prevents the sterilant from effectively reaching and killing these spores on the spore disc.
Other disadvantages of the prior art products are that the sealed ampule is broken and the fluid medium flows into the tube to contact the spore disc. The imperfectly sealed containers permit spillage of the culture medium. The spillage may result in the spreading of the contaminated culture medium. Also, the ampules of the prior art products contain a small volume of culture medium such that, when the prior art product is placed in the incubator, the elevated temperatures of the incubator enhance evaporation of the culture medium. The volume of culture medium is so small that the culture medium evaporates before incubation is complete. Thus, the prior art product may be dried out unless it is placed in a humidified incubator. In addition, the spore carrier in the prior art products is positioned immediately adjacent the ampule in the tube. When the prior art product is placed in the sterilization chamber the ampule acts as a thermal insulator for the spore carrier. Some of the micro-organisms are protected from the sterilant and may survive sterilization.
Accordingly, there is a need in the art for a sterilization indicator which is capable of withstanding high temperature and pressure environments and which indicator device moves a test article from an open chamber into a sealed chamber containing a fluid medium while maintaining the sealed chamber in a sealed condition.
There is a further need for an indicator device wherein an open chamber containing the test article is external to the sealed chamber wherein the outside environment can enter the open chamber and contact the test article such that an adequate exposure to a sterilant is achieved and yet the sterilization does not enter the sealed chamber.
There is a further need for a sterilization indicator which defines a means for moving the test article from an open chamber into a sealed chamber and wherein the sealed chamber remains sealed at all times thereby preventing inadvertant contamination or leaking of the fluid medium from the sealed chamber.